Modern computer operating systems often provide a desktop graphical user interface (“GUI”) for displaying various graphical objects. Some examples of graphical objects include windows, taskbars, docks, menus and various icons for representing documents, folders and applications. A user can interact with the desktop using a mouse, trackball, track pad or other known pointing device. If the GUI is touch sensitive then a stylus or one or more fingers can be used to interact with the desktop.
Some computer applications include knobs, sliders and other controls that can be manipulated by a user through a pointing device or by touch input. For example, graphical objects emulating knobs and sliders of a mixing board or other hardware device can be included in the GUI of an audio or video application. The user can use a mouse or finger to rotate the knob control or move the slider control as desired to control a parameter of the application.